I need christian advise please?

[wildflower]

I would not apologize to anyone how I came to discover about your sister's double life. I would get my sister alone and let her know what you found out about her double life. Let her know that you will expose her, if necessary, to the parents and authorities if she doesn't stop this behavior. Be prepared to go to Child Protection Services if necessary. I wouldn't threaten to do this... I actually would go forward with it if she doesn't co-operate. It is for her own good.

If you think she will stand up against you on this, then go ahead and go to the CPS without even notifying her on this., Your decision. She's not gonna like it and she may put up a hard fight against you. Do what ever is best for your sister.